Custom "payloads"

[nicob at nicob.net (Nicob)]

Hi,

I'm actually working on a Metasploit plugin which is exploiting a
SQL-Injection vulnerability. I don't have command or shellcode
execution, but raw access to the underlying DB can be used to create a
new admin account, modify the password of an existing admin account, ...

So, I wonder how to ask to the MSF user which "payload" (ie. SQL query)
he wants to execute. I can add a text field to 'UserOpts' and parse it
later to get the selected payload, but I'm not sure it would be the
cleanest way to do it. Any advice is welcome. 
  

Nicob